AUTHOR=Clare Alison J. , Day Robert C. , Empson Ruth M. , Hughes Stephanie M. 

TITLE=Transcriptome Profiling of Layer 5 Intratelencephalic Projection Neurons From the Mature Mouse Motor Cortex

JOURNAL=Frontiers in Molecular Neuroscience

VOLUME=11

YEAR=2018

URL=https://www.frontiersin.org/journals/molecular-neuroscience/articles/10.3389/fnmol.2018.00410

DOI=10.3389/fnmol.2018.00410

ISSN=1662-5099

ABSTRACT=<p>The mature cortex contains hugely diverse populations of pyramidal projection neurons (PNs), critical to normal forebrain circuits. In order to understand the healthy cortex, it is essential to characterize this neuronal complexity. We recently demonstrated different identities for <italic>Fezf2</italic>-positive (<italic>Fezf2+ve</italic>) and <italic>Fezf2</italic>-negative (<italic>Fezf2−ve</italic>) intratelencephalic-PNs (IT-PNs) from layer 5 of the motor cortex (M1). Comparatively, each IT-PN type has a distinct electrophysiological phenotype and the <italic>Fezf2+ve</italic> IT-PNs display a unique apical dendritic tuft. Here, we aimed to expand our understanding of the molecular underpinnings defining these unique IT-PN types. Using a validated <italic>Fezf2</italic>-GFP reporter mouse, retrograde labeling techniques and fluorescence activated cell sorting (FACS), combined with a novel approach for low-input RNA-sequencing, we isolated mature <italic>Fezf2+ve</italic> and <italic>Fezf2−ve</italic> IT-PNs for transcriptome profiling. Through the comparison of <italic>Fezf2+ve</italic> and <italic>Fezf2−ve</italic> IT-PN gene expression profiles, we identified significant enrichment of 81 genes in the <italic>Fezf2+ve</italic> IT-PNs and 119 genes in the <italic>Fezf2−ve</italic> IT-PNs. Term enrichment analysis of these enriched genes demonstrated significant overrepresentation of the calcium-binding EF-hand domain in <italic>Fezf2+ve</italic> IT-PNs, suggesting a greater importance for calcium handling in these neurons. Of the <italic>Fezf2−ve</italic> IT-PN enriched genes an unexpected and unique enrichment of genes, previously associated with microglia were identified. Our dataset identifies the molecular profiles of two unique IT-PN types in the mature M1, providing important targets to investigate for their maintenance in the healthy mature brain.</p>